Best man catches friend's wife cheating with a barman and films the whole thing.

A video showing the agonisingly awkward moment a man catches his best friend's wife cheating on him with a barman has gone viral.

The footage, apparently filmed on a camera phone, shows a woman identified only as Nina climbing off a man's lap looking appropriately embarrassed.

The man filming - who later tells us his name is James - says: 'How you guys doing? Nina, what's going on here? 

Nina replies: 'Yep, you know exactly what's going on'.  

'Tell me what's going on, James continues, 'Who's this guy?'

'That's not your husband, right? You don't look like her husband to me.'

While Nina hangs her head, the barman she is with starts shining the light on his phone at the camera so he cannot be identified in the video.

James says: 'That's a good idea. I don't blame you. I'm James, I was the best man. This is Nina, this is my best friend's wife. So are you the bar tender?'

He replies: 'Not only, but yes.'

'Okay, that's excellent, James responds. 'Well you guys have a good night.'

The video then cuts out.

The footage, which has already been viewed more than three million times on YouTube, was posted on Reddit with an explanation that the husband had married the woman in a 'spectacular wedding' a year and a half ago.

But, suspecting his wife of cheating, he had apparently asked his friend to follow her and see what she was up to, having heard which bar she was going to that night.

The text explaining the video stated: 'After finding out, the husband went home, took the car, took her ring, and told her she had until the end of the day to move out.'